Mongolian visa in Kazakhstan should be no problem. I received one in Almaty. I have also got one in Ulan Ude. I don't think it's anything to worry about.

For the Russian visa, you should be able to get transit visas in Kazakhstan (I got one in Oral). Not sure about tourist visas at present; it's much better to leave home with a multiple entry Russian visa.

Iranian visas can be issued at any embassy / consulate theoretically. I have got them in London, Bishkek, Islamabad, Munich and Yerevan. All you need to do is tell the agency which embassy / consulate to send the visa invitation to.

Turkmenistan should be the same, though some may be easier than others. I have got them in Tashkent and Mazar-e Sharif (applying in Kabul). Last time I went, I got a visa reference code from the embassy in London and got the visa at the Kazakhstan - Turkmenistan border.

The Russia - Belarus border is, according to official information, only open to foreigners at the Novy Yurkovichy border post in the far south (a triple border crossing between Belarus, Ukraine and Russia). I crossed the Belarus - Russia border freely in 2010. There is no border control, so it's like driving from The Netherlands into Germany, which is why, it seems, foreigners are no longer allowed to cross here. I'm not sure if it's really true, but you don't want to be caught in Russia illegally. Therefore I would advise you either to use the birder I mentioned (southern Belarus is rather pretty) or head up into Latvia and then into Russia. You could stop in Pskov which is a lovely city.

EO

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EurasiaOverland a memoir of one quarter of a million kilometres by road through all of the Former USSR, Western and Southern Asia.