Hello, is this sentence correct?

A sentence starts with a capital letter and ends with a full stop (or other stop), so this cannot be a sentence.

What you've written is ungrammatical because there are two main verbs ("is" and "has become"). These are possible:

"It is without a doubt a popular destination."
"It has without a doubt become a popular destination."

good

so it is not possible to have two verbs in one sentence, am i correct?

edyguardsso it is not possible to have two verbs in one sentence, am i correct?

Sentences begin with a capital letter. The word "I" is always capitalised.
It is not possible to have two main verbs in one clause. It is common to have two or more verbs in a sentence.

"He fell and broke his leg."
"My arm hurts when I move

edyguardsso it is not possible to have two verbs in one sentence, am i correct?

No, it's possible for a sentence to have more than one verb, and even more than one main verb.

Your original sentence contains three verbs:

1. is -- (presumably) a main verb
2. has -- an auxiliary verb
3. become -- a main verb

The problem is that

it is quite interesting, let me ask one more question,

is it possible to have a sentence like

(1)
it without a doubt is a popular destination or

(2)
it is without a doubt a popular destination

which one is the subject?

in the first sentence

is it really okay to say that the subject is it without a doubt

Have you even bothered to read any of my replies? I have explained twice now that A SENTENCE BEGINS WITH A CAPITAL LETTER AND ENDS WITH A FULL STOP (OR OTHER STOP).

Sorry, now this should be okay since i have written a sentence begun with a capital letter and ended with a full stop.

Thank you for your explanation, can you answer my last question below?

The subject is "It". The "without a doubt" part is just an additional remark that can be left out without affecting the grammar of the sentence.

So it should be okay to have a sentence "it without a doubt is a popular destination".