Past tense reflexive verbs
Can anyone give some examples of the above and an explanation please?
Is it a case of learning the verbs that are reflexive or is there a way of knowing when to use a reflexive?
Ich wusch mich. Du rasiertest dich. Er setzte sich.
I washed myself. You shaved (yourself). He sat down.
Past tense has nothing to do with reflexive or not. For learning, you might just stick to learn it for each word and not by a rule, but if you want a rule/guideline, then: for most cases where the subject and the object of the action are the same you have to use a reflexive pronoun, additionally there are a few exceptions, which cant be explained by this in modern german and which also use a reflexive (likely because in older german they followed this rule). Example: - Ich freue mich dich zu sehen. I am happy to see you. Very likely it was once (long long time ago) something like Ich erfreue mich (which would be ultra strange to say nowadays, but you can still say Ich erfreue ihn mit Blumen / I make him happy with flowers in modern german).
Ich wasche. Ich wasche mich. Ich wasche das Kind. Im washing (not stated what gets washed). Im washing myself. Im washing the child.
An example of a reflexive verb is "sich beeilen" (to hurry).
Present tense: Ich beeile mich.
Past tense: Ich beeilte mich.
Present perfect: Ich habe mich beeilt.
In general, present perfect is much more used in modern German than past tense. So for anything that happened in the past, you will most likely encounter "Ich habe mich beeilt".
The second part of your question ... I don't know. There are reflexive verbs (like "sich beeilen") that can only be used that way.
And there are verbs that take a dative or accusative object, and that can be used in a way that simply refers back to the subject. For example "waschen".
Ich wasche die Pullover. (I wash the sweaters.) -- Normal accusative.
Ich wasche mich. -- Reflexive use of the verb "waschen"
Ich helfe meinem Vater. --- Normal dative
Ich helfe mir. -- Reflexive use.
(Cross-posted with MortiBiRD)
Edit: This University Michigan link looks very interesting -- it also includes a list of verbs https://www.lsa.umich.edu/german/hmr/Grammatik/Reflexiv/Reflexiv.html)