There is no one "Soviet model". There are several models: War Communism, NEP, "Stalinist" economy, Khrushchev Revisionism, Brezhnev Revisionism, and Perestroika.
I'm talking about "Stalinist", obviously. But it had co-ops that operated within market economy (eradicated in late 1950s by revisionists), so I'm not sure what you mean. Kosygin reforms?
How? Explain to me what mechanism Market has, Planning doesn't.
Nope-nope-nope. First and foremost, plans are priorities. You have general goals (build industrial cluster that will produce something; which means you need hydro plant there and nuclear power plant here;), the rest are guidelines. It's obviously more complicated than that, but it's not some inflexible time-table you have to follow to the letter or everything goes kaput.
Democracy sets goals and gives promises ("we promise to produce that much of this stuff, so you can count on us", for example). The rest is job of managers.
Planning can use price. It's just inefficient to be bound by price alone (which is the curse of market). Which is why markets go belly-up without finance (it exists to circumvent problems price causes).
If I order car next year, producer can be certain that he can sell car to me.
There isn't one set "planning".
First phase would be NEP-like State Capitalism with pre-existing corporations being managed by state and overseen by people's commissars (grass-root investigations - RabKrIn, if you know what I mean). That could take 5-10 years, depending on circumstances. It should be easier to manage today, but we have less actual (non-cultist) economists.
Second phase would be actual Socialism (what I often call "Soviet model", implying apex of USSR economy - which is generally referred to as Stalinist economy; hence my icon), with centrally-planned economy doing the heavy lifting (industrial goods, infrastructure, most of research, medicine, some basic consumer goods). Co-ops are a minor factor (overseen by state; mostly consumer goods; 5-10% of economy). That could last 20 years easy. Probably more, since we don't have a concrete idea on what should be done after, other than "create more productive forces".
Third phase would be transition to actual Communism, with more and more goods being freely (or "socially", so as to differentiate from unreasonable demands) available.
This is Holla Forums.
Yes. Read Lenin.