Are Reservists only held to Army Regulations on weekends during drill or 24/7 like those on active duty?

OK, great stuff on being squared away all the time. Technically you are only subject to UCMJ, Regs, etc. when you are on inactive or active duty only OR.... The "OR" piece is if you do something bad off duty that relates to the MIL side of the house. I had a LT that decided to put his uniform on and join up with other anti war protesters and crash their Congressman's home office. Wound up on the 6 o'clock news. Had another Seabee decide to go to the compound and "borrow" a backhoe to dig himself a pool at home. So there's lots of ways to get into trouble. What the lawyers do is establish a legal connection of the off duty behavior that allows for the MIL side to take action.

There are other non military regulations that you are subject to. The Hatch Act means you can't put your uniform on and campaign for a Pol. Bottom line, it's better to be squared away all the time so you avoid testing that line where they can reel you in.

Let's just set regulations aside for a moment. Regardless of whether or not you (any SM really) happen to be on Uncle Sam's payroll at a given moment during the time you are a Reservist under contract, your behavior--24/7/365--leverages the reputation of the Army Reserve. Make the headlines--good or bad--and you can rest assured your affiliation with the military will be noted for all to see.

Without drowning in the minutia of regulatory interpretation, you should know what doing right is, so as a reasonable person if you go with that, you'll be fine. Better to remember this than memorize some Army Regulation for an ex post facto argument.

Do you have to be clean shaven every day? No.
Do you have to PT every day? Again no (but you should still work out so that you can maintain Army standards).
But just because you're not in the Army 24/7, doesn't give you free reign to go out and drink yourself to death or smoke a bowl!