Can I fill normal INK Pen ink, into Epson printer cartridge?

I think you can refill your printer cartridge using Ink and an injector. When you buy this you'll get proper instructions on how to inject ink;)

No, pen ink is formulated differently. Its not made to withstand the heat and pressure exerted by the print heads.

Be very careful with an Epson or other printers with a separate print head. Clog it up and you will be paying more for a new print head than the printer cost. If you mess up the print head on an HP cartridge, you can replace it for the price of a cartridge.