Crock pots and hotplates

Question

Rabbi Abadi As you know I am in a process of teshuvah and have many questions which may seem simplistic to many. I appreciate the care with which you answer my questions and the patience you have with me. Hopefully I will not push that patience with the following, seemingly simple questions. 1) Can I use a crock pot or electric hotplate to keep cooked foods (cholent, kugel, etc) warm on Shabbat? 2)What, if any issues, do I need to consider in terms of the type of crockpot or hotplate. I've read differering opinions depending upon whether the heating element surrounds the crock pot or is only under it. 3) Do I need to cover the hotplate with foil (or even line the space between the crockpit and the heating element with foil? 4) Must I remove the pot from the hotplate or crockpot base before serving. 5) Is there any issue with me returning the pot to the hotplate or crockpot if I intended to do this from the beginning. 6) In regards to hot water. Is it permitted to use an electric thermos to keep hot water warm and are there any restrictions here. 7) I have read conflicting opinions as to whether I can add hot water directly to instant coffee from a thermos or need to transfer from one cup to another and sometimes to a third. 8) Does it matter if I put the coffee in first or the water in first? Thanks again for all of your guidance. Jim