hi pal.from your message i can derive that you like charizard(me too) and just want it in your rom. Now there was a time i was in same situation. I wanted all my favourite pokemons in one rom,but cannt get any hack to provide me that. I was desprate,i read on net,watched youtube videos,there was this one hacker-jambo51 and shinyabsol,they helped me,it was a thing I just wanted. And now I have entered my own sprites of kyurem,kyurems both forms,rath and benmummy from ben 10,jinpachi mishima and nina etc from tekken game and lots of fakemons in addition to various 4th and 5th gen pokemons in my fire red rom. I have inserted over 100 scripts,maps etc. And am still doing more. So,if you have passion,just find on net(poke community) is a great site.look in tutorial section for your needs. Read there,watch on youtube,and try one thing at a time.
As for your request-not only can you enter silver version charizard in your rom,but you can also enter any sprite you wish. How-
1.i do all work in fire red gba rom,so if it were for a gba rom I could tell you exact names,but as your game is a gb/gbc rom ...ok firt do a thing-
1.search net,use google or you can find on this site(pokecommunity.com),swampert tools,etc,there are gb/gbc hack tools.
2.look for a tool description to enter new sprites in a rom. I will update this tools name after i find it.
3.download that tool.
4.choose a sprite of your fav pokemon.you will easily find them on net.there must be two images,one front one back.
5.Now you remember the software i said,to insert pokemon sprites...open it,load your rom,and select any pokemon.example bulbasaur...
6.thern click file,and there must be a option to save this image of bulbasaur.save on your desktop.
7.minimize this image inserting software for now.
8.look at the image you saved. .check its size. I think its 8x8 or 16x16(not sure). So your new image shall be of this size only.
9.download a software called irfanview(must have)..open your new image in it.press cntl+ r to resize it,and resize it to the size you got of your games sprite.ie.of bulbasaur. Ex.16x16
10.now in irfanview only,decrease image color to 16.and save the image on desktop.let it be image 1
11.now goto change pallete and rlace first color of you sprite to the background color and save this image as indexone on desktop.let this be image 2
11.open your image 1 in ms paint(the one you get in windows XP and not win7 one,as it would not work).once opened,select all and copy.
12.open image 2 in other mspaint and paste image 1 on it.
13.your messed up image 2 will turn fine. Save it.
This is an indexed image.if you didnt got it,read in pokecommunity tutorial section,how to index a image.many good tutorials are there.
14.similarly create an indexed sprite for your back sprite.
15.now open your image inserting software,goto any pokemon you want change,ex charizard,cthen click file,import image
16.import your indexed images,and click save.
17.you might also need to have free space finder software if it says image size too big aborting.
18.as i said i work only on gba rom,so i might not have helped you much,if you get your job done,i shall be happy. If not pm me and i will post it with pics.and tutorials.
Till then...bye.and make sure you geet your charlizard inserted.