Хотя киви и кислый, мне всё равно нравится его вкус.

In Хотя киви и кислый, the и is not a normal and. It is a particle used in the pattern хотя ... и ..., which means although ... still / even though ....

So:

• Хотя киви кислый... = Although kiwi is sour...
• Хотя киви и кислый... = a slightly more idiomatic and emphatic version of the same idea

The sentence would still be grammatical without и, but with и it sounds very natural.

Because киви is an indeclinable borrowed noun, and in standard Russian it is usually treated as masculine when referring to the fruit. So the adjective agrees with it as masculine singular:

• киви кислый

Even though киви ends in -и, that ending does not tell you its gender here, because the word does not decline like a typical Russian noun.

You may sometimes hear other agreement patterns in casual speech, but кислый is the safest standard choice.

Yes. For food, кислый commonly means sour.

So in this sentence, it describes the taste of the kiwi as tart or sour, not just chemically acidic. This is exactly the normal word Russian uses for sour-tasting foods.

Russian uses нравиться differently from English to like.

Literally, мне нравится его вкус is closer to:

• Its taste is pleasing to me

So the structure is:

• мне = to me
• нравится = is pleasing / appeals
• его вкус = its taste

You could say Я люблю его вкус, but that sounds stronger, more like I love its taste. Мне нравится его вкус is more neutral and very common.

Мне is the dative case of я.

That is because нравиться takes:

• the person who experiences the liking in the dative
• the thing liked as the grammatical subject

So here:

• мне = to me
• вкус = the thing that нравится

This is one of the most important patterns to learn in Russian:

• Мне нравится чай.
• Ему нравится музыка.
• Нам нравятся книги.

Because the grammatical subject is вкус, which is singular.

In Russian, нравиться agrees with the thing being liked:

• Мне нравится его вкус. = taste is singular
• Мне нравятся фрукты. = fruits is plural

So the verb form depends on вкус, not on мне.

Here всё равно means still, all the same, or nevertheless.

It shows that the speaker’s opinion does not change because of the sourness:

• Хотя киви и кислый, мне всё равно нравится его вкус.
• Although kiwi is sour, I still like its taste.

Be careful: мне всё равно by itself can also mean I don’t care, but in this sentence that is not the meaning. Here it simply adds the idea of despite that.

Yes, вкус киви is also possible.

• его вкус = its taste
• вкус киви = the taste of kiwi

Both are natural. Его вкус is shorter and refers back to киви. Since киви is not a person here, его means its.

Using вкус киви can sound a little clearer if you want to avoid any possible ambiguity.

Because свой would likely point back to the speaker in this kind of sentence, not to киви.

So:

• мне нравится его вкус = I like its taste
• мне нравится свой вкус could sound like I like my own taste or my own sense/style/taste

To refer clearly to the kiwi, его is the better choice.

Because Хотя киви и кислый is a subordinate clause introduced by хотя.

In Russian, a subordinate clause is normally separated from the main clause by a comma:

• Хотя киви и кислый, мне всё равно нравится его вкус.

This is the same basic idea as in English:

• Although kiwi is sour, I still like its taste.

Yes. Russian word order is flexible, though different orders can change emphasis.

For example, you could also say:

• Хотя киви и кислый, его вкус мне всё равно нравится.
• Мне всё равно нравится вкус киви, хотя киви и кислый.

The original sentence is very natural. It first gives the contrast (although it is sour) and then gives the main point (I still like its taste). That makes it sound smooth and idiomatic.