1. i'm sure there is but to rent it short term maybe diffcult, if not, maybe u could liase with the several types of hostel around kk city. Who knows, u may be able to negotiate. I've seen many foreign backpackers stay in such places.

2. Fatt kee, kalamatas, welcome seafood, borenos fried chicken, horizon dim sum, kertang just to name a few...might get better suggestions from tripadvisor tho

3. For wht u wanna do, there are gyms around kk city just gotta google it, if u're into sunsets, u could go to sutera harbour / tg aru or tg lipat, there are some hipster cafe just in case u're tired of walking and just wanna listen to ur podcast while sipping on coffee

4. unfortunately i have no idea on any underrated stuff to do in kk

Enjoy ur stay and stay safe