Answer:

Most effective would be to attack it when it’s connecting to the cells. The least would be to attack the HIV protein chain.

which targets would be most effective in blocking HIV infection

The most effective target would be the one that would completely stop the virus from binding to the T cells.

HIV attacks T-helper cells, which are white blood cells in the immune response. This pathogen first binds to the T-helper cell, then merges with it, seizes command of its DNA, duplicates itself, and distributes additional HIV into the bloodstream. HIV is incapable of reproducing by itself. Alternatively, the virus binds to and merges with a T-helper cell. It then tends to take over the cell's DNA, replicates itself within the cell, and ultimately discharges more HIV. HIV binds itself to a T-helper cell. It then unites with the cell and transmits its genetic data. Because they prevent HIV from entering the cell, medicines that block this step of the lifecycle are known as fusion or entrance inhibitor therapies. The HIV lifecycle is the process through which HIV multiplies and enter the bloodstream. Anti-HIV medicines target distinct stages of the HIV lifespan, thus understanding how HIV enters the body can aid understanding of the many preventive and therapy choices. 

what target is the  least effective in blocking HIV virus

A target that would be the PR enzyme 

The use of a variety of inhibitors that target these enzymes can decrease viral burden and postpone disease development for a long time. Problems of antiretroviral therapy, such as the advent of viruses impervious to existing medicines, are pushing the creation of additional antiretroviral therapies that target not just the restoration and protease enzymes, but also unanticipated targets.

References;

Schopman, N. C., ter Brake, O., & Berkhout, B. (2010). Anticipating and blocking HIV-1 escape by second generation antiviral shRNAs. Retrovirology, 7(1), 1-13.

Klasse, P. J., Shattock, R. J., & Moore, J. P. (2006). Which topical microbicides for blocking HIV-1 transmission will work in the real world?. PLoS Med, 3(9), e351.

Rybarczyk, B. J. (2002). Abracadabra: Magic Johnson and Anti-HIV Treatments. National Center for Case Study Teaching in Science.

Murooka, T. T., Deruaz, M., Marangoni, F., Vrbanac, V. D., Seung, E., Von Andrian, U. H., ... & Mempel, T. R. (2012). HIV-infected T cells are migratory vehicles for viral dissemination. Nature, 490(7419), 283-287.