Learn English – The difference “do you think so?” and “do you think like that(this)”

I have to disagree. Grammatically, the sentence is doing no more and no less than asking to what extent the other person likes the shirt.

Compare: How do you like your boss?

This does not imply any favor or disfavor on the part of the person asking.

That said, practically speaking, when you ask someone about a shirt, you are typically considering buying/wearing it, and thus typically have at least a semi-positive opinion of it. But that's true of all your example sentences.

Yes. This:

… and then you can make your own siphon

literally means this:

… then you can make a siphon which will be your own

And it suggests very strongly that you will make the siphon by yourself—in other words, that you will make the siphon on your own. It really just means the same as:

… and then you can make a siphon.

Here's what's going on.

"Your own X" means the same as "Your X"; the word "own" just adds emphasis. For example, if you save enough money, you could own your own car—as opposed to driving a company car, using taxis, etc.

To do an activity on your own means to do the activity by yourself, or at least without the usual kind of supervision or guidance. There's no noun after "own". For example, you can learn English on your own instead of taking a class. "On your own" is different from "your own X".

When you "make your own X", the literal meaning is that you make an X, which naturally is your X. Whatever you make, normally it belongs to you, since you made it. And since you made it, you probably made it by yourself. So, "your own" is redundant. The extra phrase "your own" emphasizes you, separate from other people. This emphasis on you suggests strongly that you will make the object using amateur methods, as opposed to purchasing it from a manufacturer or hiring a professional to make it for you.

"Make your own siphon" is slightly playful, since (I think) most siphons are made from whatever materials are at hand, not bought from manufacturers. Normally, people say "make your own X" when talking about how to make something that's usually made in factories. For example, here is a book titled Make Your Own Electric Guitar. Since electric guitars are normally made only by professionals, the title of the book clearly means that it provides instructions for an amateur to make an electric guitar.