Chair-and-standing yoga for 60+

I'm a man in my early 60s, new to yoga, and I want a gentle 20-minute yoga session that mixes seated (chair) and standing poses to improve my flexibility and balance and help me wind down. I'll keep a sturdy chair nearby for support during standing poses. Please give me a sequence with clear hold times in seconds for each pose and simple breathing cues. Include: 1) A 3-minute seated warm-up: easy neck and shoulder rolls, seated cat-cow, and seated side bends, with hold/breath counts. 2) A 12-minute main sequence of beginner-friendly poses, alternating seated and standing-with-chair-support: seated forward fold, seated spinal twist (each side), chair-supported standing forward fold, chair-supported standing balance (hold the chair, lift one heel), gentle standing backbend, and a chair-supported standing hamstring stretch. Give hold times of 20-40 seconds per pose, both sides where relevant, and tell me to never push into pain — only a mild, comfortable stretch. 3) A 5-minute cool-down: seated deep breathing and a final relaxed seated rest, with timing. Keep it calm and low-intensity, and remind me to breathe slowly throughout.