The issue at question here is whether the company can turn the loaned
property (especially property which has the potential for appreciation
such as gold) into cash and use it for expenses during the term of the
loan with creating a taxable event for the borrower.
I am focusing on the quoted material, rather than one the subquestions 1-3, because I think it provides a better foundation to explain the relevant legal doctrines without getting sidetracked too badly away from the central idea.
The primary statute governing the tax treatment of this transaction Internal Revenue Code § 1001(b) (i.e. 26 U.S.C. § 1001(b)), since no exceptions for tax free exchanges of property apply. Back when U.S. currency was on the gold standard, an analysis of Internal Revenue Code § 1037 would have been necessary, but that ceased to be the case on August 15, 1971, more than half a century ago.
Ultimately the terms of the loan instrument would control.
But, it would be almost unheard of to make a loan denominated in gold, however, that is a true loan creating a debtor-creditor relationship between the parties, as opposed to (1) a pledge of the gold as collateral for another loan, or (2) as a bailment authorizing the person getting the goal to keep in in their possession temporarily with or without a fee for doing so (this would rarely be done for gold bars, but would be not terribly uncommon for fine art or jewelry or ultra-expensive designer or historically important clothing, for example, for a theatrical production or to make an office of a firm look pretty).
Usually, rather than "loaning" a gold bar to a company, what someone who wanted to provide financial assistance to the company (e.g. a shareholder) would do would be to allow the gold to be pledged as collateral for a loan of money from someone else who can make a loan in dollars (assuming a U.S. case). The security agreement pledging the gold as collateral would almost never authorize the creditor to sell the gold except in the event of a default on the loan.
In the absence of a default on the loan, the gold would be returned without being sold, when the loan of cash for which the gold was collateral was repaid in full.
If there was a default on the loan, the creditor loaning the money with the gold as collateral would then seize and sell the gold in satisfaction in whole or in part of the debt (and trigger capital gains taxation on the part of the party owning the gold bar which was pledged as collateral), pursuant to the rules of Article 9 of the Uniform Commercial Code.
The gold bar serving as collateral would usually either be placed in a safe deposit box at a bank, or a safe belonging to the creditor or an attorney connected to the transaction, or would be kept with a firm that is in the business of storing gold for third parties, which would issue a negotiable warehouse receipt for that gold bar (governed by Article 7 of the Uniform Commercial Code). If a warehouse receipt was issued, the piece of paper that is the warehouse receipt would then be held in the safe deposit box at a bank or safe belonging to the creditor, rather than actually putting the gold bar itself in that place (especially if it isn't one gold bar, but hundreds of gold bars that take up lots of space).
This is because, usually, third-parties don't accept gold, in kind, in transactions. I've never seen in more than 25 years of practicing law in the U.S., a lease, or a car loan, or a mortgage, in the modern U.S. (as opposed to 17th and early 18th century documents), that provides for payments to be made in gold in anything but a gold mining contract where it functions as a good produced and not as a currency substitute. Almost all legal obligations in the U.S. are denominated in U.S. dollars instead.
Alternatively, the person with the gold would sell it themselves, pay the taxes, and loan money to the firm rather than gold.
Tax law is designed to discourage in kind true loan transactions by triggering taxation when the item loaned in kind is sold, in order to encourage firms to do business in U.S. dollars which is the way that our economy and its rules are designed to work legally.
I suspect that this question is motivated by its analogy to cryptocurrency transactions of the same character, and the analogy between cryptocurrency transactions and gold is a sound analogy for almost all non-trivial purposes (and the analogy of a warehouse receipt for a gold bar to a Bitcoin is even more exact).
Footnote
If the borrower of the gold bar sold it in violation of the agreement between the parties, and the lender brought suit to rescind that transaction, the taxpayer could probably defer the capital gains taxation as a result of the sale while the litigation was pending, and could probably escape capital gains taxation entirely if a court rescinded the transaction in the course of that litigation. But if the gold bar was sold to a BFP (bona fide purchaser for value), the lender of the gold bar probably couldn't successfully rescind the transaction.
The money damages awardable in a breach of contract lawsuit by the lender against the borrower for causing the lender to prematurely pay income taxes on the accrued capital in the gold bar due to a sale in breach of the contract would not usually be damages (since they would ordinarily be due sooner or later anyway, unless the lender of the gold bar could convincingly argue that it would otherwise have been held without being sold until the lender's death at which point all unrealized capital gains would no longer be taxable due to the step up in basis at death).
But, an actuary or accountant could probably quantify the lost time value of money associated with having to pay those taxes sooner rather than later, although that would be a comparatively small amount.
