Theres a Mk1 and Mk2 Clio (sometimes called Clio 1 and Clio 2). Mk1 was 1991-1998 and Mk2 is 1998-present.
There were 3 "phases" of the Mk1 Clio and so far there have been two phases of the Mk2 Clio.
The Clio Mk1 phase 1 and 2 (1991-94 and 94-96) were similar, with only minor changes - there was a phase 3 (96-98) as well, where the most sporty models were dropped and the changes to the bodywork were more radical.
The Clio Mk2 phase 1 (1998-2001) and phase 2 (01-present) look quite a lot different and have different rear suspension. However, because the platforms are the same, the newer model is a "phase 2" rather than a "Mk3".
The Clio RSi was avaliable throughout the Mk1 period. It was an 8v 1.8 with 110bhp, sports trim and side skirts - the hot hatch was the 16v (the Williams was a special edition of the 16v with some drivetrain/colour changes). There was an RSi for a time in the Mk2 Phase 1 Clio - it was a 1.6 16v with 110bhp: its now called the 1.6 Dynamique.