Can new patio be put over existing base?

[tarajirving]

Hi we have just had an old sandstone patio ripped up and a new porcelain one will be put down. The person doing the job has said the existing base will be fine to use. There are a couple bit he will need to level out but aside from that, he will clean the area and relay. I have attached some pictures as I am not convinced so looking for on advice on whether others think the base is OK? Thanks.

 

[Harvey]

Hi, I am a DIY. I am building outdoor BBQ with countertop and cabinets. I wrapped it all in plywood. My question is :
what is best adhesive for it so as to stone sides and tile on counter top. Will it be good enough or will plywood have problems later. Thank you very much for your help,