eurasiaoverland already covered it well.

A few considerations (some of it might be out of date, but perhaps helpful in general):

Have you worked out your route yet fully? Sounds like you are still at an earlier planning stage?

From your original post it sounds like Armenia - Iran - Turkmenistan - Uzbekistan - ... In that case, note that you cant cross from Uzbekistan into Pakistan, nor can you from Kyrgyzstan, nor Tajikistan. Taking the silk route option with the Stans is beautiful and rewarding, but it will include either crossing China (Xinjang!) which is it's very own hassle (I speak from experience, I took this route). A fallback can be air freighting Bishkek to Delhi or Almaty to Delhi. If you go this way, it may also be possible to get a transit visa for Turkmenistan, which is significantly cheaper than the tourist visa. However, it requires you having the visa for the two neighbouring countries (Iran and Uzbekistan) in your passport at the time when you apply for the Turkmeni visa. In addition, the transit visa will have fixed dates on it and give you only 3-4 days, so you need to be on time. It is possible to apply for the transit visa in Tehran and pick it up in Mashad (I did that), but there might be some hoops to jump through to get the Turkmeni officials to play ball and let you do that. I think I had to go to the Turkmeni embassy in Tehran at least three times, and in the end had some help from another embassy.

You then mention Iran - Pakistan. Many have taken that route and you will find a lot of info on there. In that case you would either need to go North from Georgia, with Abchasia, Russia, Kazakh etc... or skip the idea of the Stans. I'd think if you go Iran - Stans - back to Iran, that would be A LOT of visa hassle to get visas twice for many places that can be quite an effort.

In any case, once you get to Pakistan, you definitely want to take the time to travel the full length of the Karakoram highway, and perhaps budget some time to branch off into some of the side valleys (eg Skardu). It's some of the most beautiful riding I have seen on earth.

For the transit visa, yes you need the visa of both countries in your passport (ie Iran and Uz). I am not sure if they will grant you a transit visa from Kazakh to Uz, because they share a direct border. On that route, you would likely need the tourist visa.

For the tourist visa (which costs more and might require an agency and a guide that travels with you), there is no requirement on neighboring visa as far as I know.

Just saw this https://www.horizonsunlimited.com/hu...borders-102461 - important to check

No, in 2017 we got denied in Teheran.

And also we met lots of other travellers, which got denied there.
Some waited for several weeks

Not entirely correct, Iran does not stamp visas in passports, for UZ you require only proof that your nationality is approved for VoA.