This link might give you a bit of info - click on the "facilities" tab.
https://www.firstchoice.co.uk/holiday/accommodation/overview/Playa-de-las-Americas/Hotel-Best-Tenerife-002635
We've stopped in all inclusive in Tenerife and the hotel was only 2-3 stars and we got a kettle, fridge and microwave in our room; so I'd be surprised if there wasn't one in your hotel.
Usually food and drink in the restaurant can't be taken away; but anything you get from the poolside and other bars are meant to be taken away and consumed wherever you want, so taking them back to your room shouldn't be a problem.
With you being all inclusive, I also can't see a problem of asking for hot water and milk.
As for the food selection, it'll all depend on the hotel, but generally speaking there's a wide selection on offer, catering for all palates.
We usually stop at the same hotel and there is a mixture of people - some on all inclusive and some on self catering, etc. The last time we were there, we found out something new ...... the vodka that the all inclusive people get is 23% .... the vodka that paying customers get is 40% (Smirnoff). I know this, as one of the waiters showed me the bottles .... so if you ever wondered why you can drink more on all inclusive - now you know :)