Is Harvard a parenthetical or numerical referencing system?

What type of reference is this:

Pears, R. and Shield, G. (2019). Cite them right: the essential referencing guide. 11th ed. London: MacMillan

What type of reference is this:

Errami M, Garner H. (2008). A tale of two citations. Nature. 451(7177): 397–399.

What type of reference is this:

University of Bradford Library (2021) What is referencing and citing? University of Bradford. Available at: https://www.bradford.ac.uk/library/help/referencing/ [Accessed 6th December 2021].

What type of reference is this:

Lewis-Roylance, C. (2013). Advancing your writing skills. In: Keeling, J. et al. (eds). How to write well. Maidenhead. McGraw Hill.

What type of reference is this:

Micallef, C. (2015). Critical analysis: a vital element in healthcare research. International Journal of Behavioural and Healthcare Research, 5(1–2), 104–123.

In Harvard referencing, should the bibliography be structured in numerical order, or alphabetically by author name?

As secondary reference is...

What type of referencing system is in use here?

(4) Errami M, Garner H. A tale of two citations. Nature. 2008;451(7177): 397–399. Available from: http://www.nature.com/nature/journal/v451/n7177/full/451397a.html [Accessed 6th December 2021].