The simple answer is - you can't ! If the country has banned the importation, your weapon would be seized when it went though customs, and either returned to the country of origin - or destroyed.
Depends on the parts, and from what country. The frame (receiver) of a gun is subject to import laws.
What country?
No without appropriate export and import licencing.
As long as your country doesnt have any restrictions on airsoft guns.
Not unless you have a Federal Firearms License (FFL) and an import permit. If you want a foreign gun, get your gun store to order it for you. They need your business, too.
Of what state and country
It all depends on the Country where you live.
It all depends on the country or location where you live.
You need to contact the Phillippine embassy on this matter to see if you can even import a firearm into their country legally.
The oldest known air rifle gun was invented by Girandoni of Vienna about 1780, for the Austrian Army.
Inexpensive import
There are several shops around the country that make a living repairing older air guns. You can do a web search for "Air Gun Repair" or see the link below that list some shops.