I´m not an expert but i have done some checking for my own story...
1. Did Tsunade stay in the land of fire or did she travel all over ? If she did say in the land of fire was it just Konoha she refused to visited?
AFAIK, this is never quite specified, but it seems to be implied that she goes "all over" yes.
2. Sakura skills, unbais, was she any good , have natural talent? Just book smart or did Tsunade give her a cheating boost?
Well that´s a question without a good answer unfortunately. Sakura is one of the worst treated characters anywhere, she flipflops between competent, powerful and inept faster than a politician changes opinions. The author have repeatedly been criticised for his rather strange anti-female bias, they can be totally superpowered, but they´re always useless when it counts. Simplified but close enough.
Essentially, you will have to decide how you want your Sakura, she has shown plenty of skill at times and tends to get nerfed by fiat whenever her previously shown skill or power might affect the story.
She is allowed to shine a bit against puppetboy and not much else(and even there, she´s used AS a puppet herself).
She is repeatedly stated to have a natural talent for genjutsu, she is shown to be capable of absurd physical strength(even before training under Tsunade) and is occasionally shown as quite resourceful and capable, it´s really terribly hard to state with any kind of unbiased objectivity just what level she is at.
3. How old was Shizune when she left with Tsuande? I heard like pre-teen but an concrete figure would be nice.
Your guess is as good as mine. I was never able to locate any specific mention of when Tsunade actually left Konoha. Shizune is stated as 28 when first seen, with a graduation age of 9, that leaves a very wide stretch of possibilities.
Especially since i never even managed to confirm if Tsunade left Konoha for good before or after the Kyubi attack. The indications point towards "before", but even that is uncertain.
The Narutoverse tends to have a lot of timeline issues, important things are lost from the collective memory in a few years while we never get a clear grasp of just how long different events take, or when they take place more than a vauge "back then".
It´s very annoying, but OTOH, it means you can just go ahead and make up your own timeline.
4. I know she can fight and what not but does she know regular justsu like Naruto, Kakashi, etc etc OR does she specialized in medical stuff and is augmented with physical fighting ability ?
Shizune? AFAIK, she does not have the hyperstrength of Tsunade in any way. She does appear to know "regular jutsu" as well but the few times such is shown could be exceptions to the rule.
Personally i doubt she could become jonin, while not active in the village without knowing quite a lot outside of her specialty as well.