Is it permissible to spend mosque funds on building and furnishing a second official residence for the Imam, especially given that the Imam is collecting donations and transferring them for this purpose, and is it permissible for him to use part of the sand allocated for the mosque to build another charity?

It is not permissible to spend endowments or donations designated for a specific entity, such as a mosque, on another entity. Rather, they must be spent on what they were allocated for, out of consideration for the donor's intent. As for funds designated for general charitable causes, they may be spent on any door of goodness. Therefore, the action of an Imam who solicits donations for a mosque and then spends them on a charitable organization or otherwise, or prioritizes the interest of a dwelling over the interest of the mosque itself, is forbidden, unless the dwelling is an accessory to the mosque and is being built in a rightful manner. This Imam must be advised and reminded, and if he does not respond, then the competent authorities must be informed if there is evidence.