They were released in a lot of models variations (mostly concerning the keyboard or colour of the casing) from late1982-1983 to 1989.
While MO and TO models are incompatible in software, most of the peripherals and Hardware were compatible.
2nd generation was almost fully retro-compatible with 1st generation but specific 2nd generation softwares couldn't run on 1st generation computers.
Those compatibilities issues were fatal to the range alongside the success of the Amstrad CPC in France.
Most TO computers were supplied with a light pen, or even mouse (TO9) for the later generations.
The varied ranges were plagued by inconsistencies in releases, alongside a bigger price than Amstrad's products.
Many models were actually re-released better and with bugs fixed, and often more inbuilt features the year later., for a cheaper price !
As a result, peoples were shy and reluctant to get into this because those computers were not the best for the same price on the market, to begin with, and because it is always a shame to see that if you waited a bit more, you would have had a far better product.
Amstrad customers had this with the CPC664.
A typical example is the TO9, which was supplied with no Monitor first, then was supplied with a colour monitor for the exact same price a 4-6 months later.
And with a lot of additional stuff 1 year after being first released (TO9+...). And TO9 keyboard was no more compatible with TO9+...