It’s the same thing.

It absolutely is not. I don’t know, maybe you’re more familiar with the US federal system (pre-Trump, because that’s a different can of worms)? If so: imagine if the president (in this case having no ability to issue executive orders, mind you) says “we should do X”. That’s all well and good, but the X must still go through the Senate and Congress, where it might fail.

Why would a country show support for the legislation and then vote against it later?

Well, because “a country” is not a singular hive-mind, is it? The government says “yes”, but their own Parliament might say “no”.

Governments have no say in what goes on in the EU Commission or Parliament. I mean, sure, most of the time the MEPs coming out of the government-aligned parties will have similar votes, but the EU elections aren’t in-step with most countries’ elections, so it’s never a 1:1 translation. And even then, many MEPs will just vote on their own.

This is such a charitable reading that it’s probably fair to assume this is OPs alt account.

Holy fuck, watch out when opening the fridge, mate, OP might jump out of it!