Not to be a jerk, but your post is a bit hard to read. As such, I am taking a shotgun approach and answering what I can, including probably using more detail than you need.
can I have more then one copy of the same Pokemon in play at the same time
Yes.
however am I able to have all 4 in play at the same time, one as my active and the others on my bench
You could have one Active and three on your Bench or four on your Bench and something else Active.
also what can I do with duplicates when there in my hand!!
Hold onto them in case something currently in play gets KO'd, or use them to meet discard costs for various card effects (like
Ultra Ball).
In Pokémon, the limits on cards you can have
in your deck are:
1) You must have at least one card that counts as a Basic Pokémon while in your hand. If it counts as one while in play but not while in your hand (like
Robo Substitute), it will not count towards this rule.
2) Because of Rule #1, that means you can have up to 59 basic Energy cards in a Constructed Format (one where you build your deck and bring it to play) like Unlimited, Expanded, or Standard. In a Limited Format (like what is used at a Pre-Release) decks are only 40 cards, so there you can have up to 39 basic Energy cards.
3) For Constructed play, anything other than basic Energy is restricted to four copies allowed in your deck
unless the card has rules text that states otherwise. For example, a few years ago there were powerful Trainers that were known as "Ace Spec" cards, and they had a rule printed on them stating you could only have a single Ace Spec card in your deck. In Limited play,
only rules text written on the card restricts how many you may run in your deck (the normal four-per-deck limit does not apply).
4) The only rules about what Pokémon you may have in play are that you need to have room for it (default field is one Active spot, five spots on your Bench), and that there is nothing specifically listed on the card itself. For example, long ago there were Pokémon that were once per deck (like Ace Specs), so you couldn't have more than one of those on your side of the field because you couldn't have more than one in your deck. I am uncertain, but there may be some cards (most likely old and no longer legal for anything but Unlimited Format play) that could have restrictions on what else is in play, but most of the time, it is just a matter of what you have room for on the field.
5) Pokémon decks often have duplicate cards, more than is needed, because extra copies improves the odds of drawing into one when you need it. Knowing exactly how few copies of something you can get away with is an advanced skill.
