However, my answer to all three would be similar with some additional provisos. Basically, no, I don't have such a spell. There are workings I would do to enhance my memory, the most effective being deep meditation to patiently allow my mind to open and the memories to gradually float to the surface. The process of recalling memories is to my mind something that cannot be forced which is why it is so unsuited to spell work. You coax memories, you don't demand from them. Its also important to understand that some memories are suppressed for a reason. This is quite often seen in victims of child abuse who bury the memories that they are unable to confront. It needs the help of very skilled mental health practitioners to bring those memories out into the open, while of course helping the individual to develop the skill and confidence necessary to deal with them.
You can however lay foundations for placing your memories in such a manner that you can easily recall them. A friend of mine wrote a guest blog on the concept of the memory palace here and it is worth reading. The idea of the memory palace is that you store your memories systematically, linked by visual association and you can then "walk through" the place you have created in your mind and have access to all the memories you have stored.
If you are seeking memories from a past life then hypnosis may well be the best step for you to take. Again I would warn that confronting memories from a past life is not necessarily an easy thing to do. Choose your hypnotist wisely and don't push yourself too far (even under hypnosis despite popular perception you do actually retain a fair level of control). Better to unlock memories gradually over several sessions than to jump in the deep end with a level of recollection you may not be comfortable with.
There are some memory spells on this resource here that may interest you. They are not really my thing to be honest - a little too much focus on instant results which like I say isn't really what memory is all about. But I enclose the link if you want to take a look.