I saw both "siebente" and "siebte" for 7th, does it have two versions?
If so, what's the difference?
The only ordinal number where two valid variations exist is "der siebte" and its more antiquated variant "der siebente":
This rule applies for all numbers counting with seven
(107.) einhundertundsiebente vs. einhundertsiebte (the und can also be omitted).
The proper answer is: it depends. On the region, age and speaker.
The correct version still is "siebente", but as already mentioned the tendency goes to the shortened version "siebte" today which arose from the Ruhr area dominating German media.
There is also a discrepancy between the former eastern part of Germany and former western part of Germany:
http://mediawiki.ids-mannheim.de/VarGra/index.php/Siebente_/_siebte
People in the eastern part still use the proper version "siebente" more frequently. And actually they are right because the word "siebte" is not the ordinal number seven, "er/sie siebte" is the simple past of the verb "sieben".
https://www.duden.de/rechtschreibung/sieben_filtern_sichten_aussondern https://en.wiktionary.org/wiki/sieben
"siebente" is very formal and pronounced, normal is "siebte".