Is there any restriction on lending stocks which are trading in the secondary market following an IPO?

No, unfortunately it is not possible to disable share lending with respect to the protection and hypothecation rules of the SEC or the Stock Yield Enhancement Program for an individual security. The only way to prevent a security from being lent is by owning all of your securities outright (no margin loan) and by not participating in the Stock Yield Enhancement Program. …

There is no guarantee that all eligible shares in a given account will be loaned through the Stock Yield Enhancement Program because there may not be demand in the securities lending markets for certain securities, IBKR may not have access to a market with willing borrowers or IBKR may not want to loan your shares…

A halt has no direct impact upon the ability to lend the stock through the Stock Yield Enhancement Program and as long as IBKR can continue to loan the stock, such loan will remain in place regardless of whether the stock is halted…

There is no guarantee that all eligible shares in a given account will be loaned through the Stock Yield Enhancement Program as there may not be a market at an advantageous rate for certain securities, IBKR may not have access to a market with willing borrowers or IBKR may not want to loan your shares…