The word 'started' is the past participle, past tense of the verb to start. The past participle of the verb also functions as an adjective. The word 'start' is also a noun. The noun forms of the verb to start are starter and the gerund, starting.
Present perfect is formed with: have/has+past participle The past participle of start is started I have started my holidays. The teachers have started their holidays. = with plural subjects. She has started her holidays. The doctor has started his holidays. = with singular subjects.
You can't make the present perfect tense with lead. You have to use the past participle of lead = led to make the present perfect. Present perfect is have/has + past participle. They have led the race from the start. He has led the race from the start.