Yes, you undo/unbutton/snap or open the snaps You fasten the hooks on your bra. You fasten a belt when you put it on, tighten it when you adjust it. Fasten is not so often used with normal clothing, you fasten your seatbelt fx. or fasten your luggage to the roof of your car. To tack is to fasten something (usually with tacks). If you're tacking a dress, you are probably in the process of sowing it. To "do up" a dress means to button it. You fasten the hooks on your dress. I don't know what the loops you're referring to are, could you be more specific?

We button and unbutton buttons. We snap and unsnap snaps. We zipper and unzipper zippers. We fasten and unfasten hooks and loops. We don't use "tack" with clothes that I've ever heard. You may hear someone say "do or undo: but these are very general and can refer to anything (buttons, zippers, etc.)